Relay circuit



Nov. 15, 1960 J. L. CONFALONE RELAY CIRCUIT Filed Jan. 24, 1957 FIG. I

FIG. 2

m m e I u A 40 k mm MW m w lw MP .w n ML: 2 v 4L .L O $$$u I N V EN TOR. JOHN L CON/79L ONE United States Patent RELAY CIRCUIT John L. Confalone, Levittown, N.Y., assignor to the United States of America as represented by the Secretary of the Air Force Filed Jan. 24, 1957, Ser. No. 636,218

1 Claim. (Cl. 317-137) This invention relates to a relay circuit and particularly to a relay actuated bistable flip-flop circuit.

In the operation of such devices as stepping relays, square wave generators and other similar devices, it is desirable to have a bistable, low energy consuming flipflop circuit.

The present invention provides a relay actuated circuit responsive to trigger impulses to change from one to the other of two bistable conditions.

In the construction according to the invention a pair of normally closed relay switches are connected in criss cross relation to a suitable source of energy so that the energization of either relay coil deenergizes the other relay coil and parallel trigger circuits energized through a trigger switch to energize the deenergized coil and operate the flip-flop.

It is accordingly an object of the invention to provide a bistable relay switch circuit.

It is a further object to provide a circuit for alternately energizing a pair of relay switches.

It is still another object to provide a relay operated flipflop.

Other objects and advantages will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which Fig. 1 is a schematic diagram of a bistable circuit in accordance with the invention, and

Fig. 2 is a diagram illustrating the operation of the circuit of Fig. 1 during its transition between stable states.

In the exemplary embodiment according to the invention a pair of substantially identical relay devices and 12 have actuating coils 14 and 16 controlling normally closed switches 18 and 20. The coils 14 and 16 have a common connection 22 to a terminal 24 of a direct current supply source (not shown).

The switch 18 includes a movable contact 26 biased to closed position against fixed contact 28. The movable contact 26 is movable to open position under compulsion of coil 14. Likewise switch includes a movable contact 30 biased to closed position against fixed contact 32 and movable to open position under compulsion of coil 16.

Fixed contacts 28 and 32 are connected to the opposite terminal 34 of the source through a common connection 36 including a stop and start switch 38. Movable contact 26 of relay 10 is connected to actuating coil 16 of relay 12 by conductor 40 and movable contact 30 of relay 12 is connected to actuating coil 14 of relay 10 by conductor 42.

A trigger circuit 44 is fed from any suitable D.C. source, herein shown as terminals 24 and 34. Circuit 44 is connected to coil 14 through a capacitor 46 shunted by a discharge impedance 48 and to coil 16 through capacitor 50 shunted by impedance 52. A trigger switch 54 controls trigger circuit 44.

In operation of the circuit with switch 38 open both movable contacts 26 and 30 will be in closed position. Then upon closure of switch 38, the coils of both relays would be energized and the relays would race. In practice it has been found that commercially identical relays have minute differences so that one will operate faster than the other and the fastest operating relay will open its switch and deenergize the other. If it is desirable that one relay always opens first a regulating impedance 56 may be placed in one of the cross conductors such as conductor 40.

The circuit has two stable states, as follows:

(1) Relay 10 energized (contacts 18 open) and relay 12 deenergized (contacts 20 closed),

(2) Relay 12 energized (contacts 20 open) and relay 10 deenergized (contacts 18 closed).

The circuit may be switched from either stable state to the other by a triggering pulse applied to conductor 44, as by the momentary closure of switch 54. When this occurs each relay coil will receive a momentary pulse through condensers 46 and 50. The energized relay will not be affected by this pulse. However, the deenergized relay will momentarily draw sufiicient current to cause its normally closed contacts to open. This will break the circuit to the energized relay permitting its contacts to close and establish a circuit from B+ to the coil of the momentarily energized relay, holding it in an energized state and completing the transition to the other stable state. Although the presence of the triggering pulse on the coil of the initially energized relay retards somewhat the release ofthis relay, nevertheless its contacts close soon enough to establish a circuit to the momentarily energized relay before its momentary energization has ceased. That this is true will be more apparent from a closer consideration of the operation of the circuit during the transition period, as illustrated in Fig. 2.

In Fig. 2, the curves I and 1 represent the behavior of the currents in coils 14 and 16 during the transition period. With the circuit in the stable state in which relay 10 is energized and relay 12 is deenergized, assume that switch 54 is closed at the instant t At this instant 1 has a maximum value i equal to the B+ voltage divided by the resistance of coil 14, and I is zero. I now begins to increase from zero, first at a maximum rate and then at a declining rate as the voltage across condenser 58 increases and that across coil 16 decreases. As the condenser charge increases further, I passes through a maximum and then declines, finally becoming zero when condenser 50 is charged to a voltage equal to B+. The maximum value of 1 is determined by the size of condenser 50, increasing toward i as a limit as the capacity of the condenser is increased. In Fig. 2, the capacity of condenser 50 is such that the maximum value of I is somewhat less than 1' In order to insure positive operation relay circuits are normally designed so that the energizing voltage produces a current in the coil considerably in excess of the minimum current required to actuate the relay. Accordingly, relays 10 and 12 are actuated at a value of current i Also, relays normally release at a value of current smaller than the minimum actuating current. Hence, relays 1i) and 12 release at a current level i It is seen in Fig. 2 that I reaches the value i and relay 12 is actuated to open contacts 20 at t When contacts 26 open B+ voltage is not immediately removed from coil 14 since it is now supplied over conductor 44 and through condenser 46 which has zero charge at t However, the current i flowing in coil 14 must now be supplied from condenser 46 and, as this condenser charges, the voltage across coil 14 and the current 1 decline, eventually reaching zero when the condenser becomes charged to the full B+ voltage. Therefore, at the instant t when contacts 20 open, I begins to decline. At 1 I has fallen to the release value i for relay 10 and movable contact 26 starts toward stationary contact 28 which it reaches after a short interval. Contacts '18, therefore, close a short time after 1 for example, at 2 It will be noted that at the instant 1 when I begins to decrease, I is still increasing and does not start to decrease until after its maximum value has been reached. Consequently, if contacts 18 were held open, relay 12 would not release until 12; when 1 had fallen to the release value i Therefore, it is seen that the closure of contacts 13 precedes release of relay 12 by an interval T.

The duration of the trigger pulse indicated in Fig. 2 is about the minimum. It may exceed this length by any amount; however, there must be a suflicient interval between successive triggers to allow condensers 46 and 50 to discharge through resistors 43 and 52.

The transition of the circuit between stable states in the opposite direction is identical to that described above and illustrated in Fig. 2, it merely being necessary to interchange the designations I and I in the drawing.

For simplicity of illustration, the utilization circuits such as auxiliary switches, current responsive devices and the like have been omitted from the drawing.

For purpose of illustration a preferred embodiment has been shown and described according to the best present understanding thereof, however, it will be apparent that many changes and modifications may be made therein without departing from the true scope and spirit of the invention. a

I claim:

A bistablecircuit comprising a pair of relays each having a set of normally closed contacts and an actuating coil therefor, a source of electrical power, a common connection between one end of each relay coil and one terminal of said source, means connecting the other terminal of said source to the other endof each relay coil through the contacts of the other relay, a capacitor having one terminal connected to the said other end of one relay coil, a capacitor having one terminal connected to the said other end of the other relay coil, means for applying a trigger pulse between said common connection and each of the other terminals of said capacitors simultaneously, and means providing discharge paths for said capacitors.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,414 Lohsse Aug. '16, 1938 2,347,481 Hooven Apr. 25, 1944 2,426,595 Busch Sept. 2, 1947 2,528,777 Persons Nov. 7, 1950 FOREIGN PATENTS 466,323 Great Britain May 26, 1937 

